1. Field of the Invention
The present invention relates to a semiconductor device and a memory device including the semiconductor device.
2. Description of the Related Art
Memory devices are now used in products in a variety of fields. In a field where high-speed searching is required such as a communication field, a content addressable memory (CAM) is widely used.
The CAM is a type of memory which stores data in each of a plurality of memory cells (hereinafter also referred to as semiconductor devices) arranged in the memory and, when reference data is input thereto, compares the reference data with the stored data in each of the memory cells to find out whether they coincide with each other. Since the entire memory can be searched in one operation, significantly high-speed searching is possible by the CAM.
The CAM is, for example, used in a database system, a set associative cache memory, and the like, in which pattern matching operation is important. A cache memory is a memory which is capable of fast access and provided between a CPU featuring high-speed processing and low capacity and a main memory featuring low-speed processing and high capacity (generally, a DRAM is used). The cache memory is usually provided with a high-speed and low-capacity SRAM (e.g., Patent Document 1).
Recently, the demand for power-saving electronic equipments has been rapidly increased in the communication field as well; thus, a power-saving CAM is expected.